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Friday, November 28, 2008

How Bad Is Acidification Anyhow?

ResearchBlogging.orgIf you've been reading the news, people are reacting strongly to a new study which reported ocean acidification due to CO2 output is occurring at a faster rate than expected. But what is the deal with acidification, anyway?

The worst part of a change in ocean pH is that it shifts the balance of carbonate ions. As the pH of the oceans drops, it is harder for animals to fix calcium carbonate. Therefore, with oceans acidifying at an alarming rate, the threat to calcified organisms is also rising faster than previously thought - and 2005 estimates were bad enough.

Luckily, some calcifying organisms have found a way to survive. Some corals can live without their solid housing, for example. When the pH drops, certain corals can live without a skeleton and become soft-bodied, retaining their zooxanthellae and acting in every other way how they normally would. They then resume building a skeleton when the pH rises again, according to a study published in science last year.

But what about the organisms scientists are most worried about, the most abundant form of phytoplankton - the coccolithophores?

The results are mixed. Some studies suggest that the pH drop will be devastating, but not all. One study found that since 1780 coccolithophores have increased the calcium carbonate in their shells by 40%, suggesting that they might be able to respond to acidification by thickening their walls.

So is all the fear surrounding ocean acidification warranted? Well, yes. Other species haven't shown the same resilience to acid waters, particularly commercially important mollusks.

All in all, the more CO2 we produce, the more we're changing our salt water ecosystems. Even if you do not believe in climate change, carbon output has and will affect the pH of our oceans, threatening the basis of the food web. So how bad is Ocean Acidification? Very bad. Very bad indeed.

J. T. Wootton, C. A. Pfister, J. D. Forester (2008). From the Cover: Dynamic patterns and ecological impacts of declining ocean pH in a high-resolution multi-year dataset Proceedings of the National Academy of Sciences, 105 (48), 18848-18853 DOI: 10.1073/pnas.0810079105

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